Where to trade/swap parts

Figured this might be the most appropiate place to ask this question; Does anyone know of a website that lists parts people are looking to trade for other parts. Outright buying and selling is easy but a lot of people out there might want to simply trade one set of tires for another set. Or maybe some hubs for a fork.

I did some googling on it but only came away with references to one-day parts swaps in certain cities.

I got the local thing in progress, along with a post on craigstlist. But the audience is just so small. Just looking for an efficient way to swap out the 26er stuff I won't be needing (frame, wheels, tires, fork...junk like that) when my 29er arrives this winter. I figure someone out there tried the 29er thing and decided to go back